Texture painting for landscape doesnt work properly

Hi, i was using a material with many layer to texture paint my terrain, but after a while i noticed that all but one single chunk of the terrain loaded the textures. I have been painting different chunks with patches of this texture but still, all loaded without problem, except for the chunk in specific where i need the texture to be.
Why could this happen? the thing i am getting is a full chunk of terrain stuck on default texture (that made with grey squares).